Peptide F is a hormone secreted from the adrenal gland. Previous studies indicated that Peptide F may be an important regulator for the immune system. Leukocytes are mainly responsible for the immune system and protect us from infectious diseases and assist in maintaining health status. In this study, the investigators are interested in the interaction between peptide F and leukocytes. There are several types of leukocytes and each has a specific role in the immune system. The primary purpose of this study is to identify which leukocytes bind to peptide F. The secondary purpose of this study is to investigate the effects of aerobic exercise on the peptide F binding of leukocytes. A greater amount of peptide F is secreted during exercise than when resting. Thus exercise may increase peptide F binding on leukocytes which could improve the immune system. In addition, the investigators are interested in the relationship between peptide F and smoking. Previously, smoking has been shown to affect the immune system and nicotine is known to stimulate the adrenal gland. Thus, peptide F may be associated with the immune system of smokers. The final purpose of this study is to examine peptide F binding on leukocytes of smokers.